General PHP

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Chapter 6 General PHP - Page 113-142

113 Adding a PHP Section to an HTML Page
116 Writing PHP Statements
119 Using PHP Variables
- 119 Naming a variable
- 119 Creating and assigning values to variables
- 120 Dealing with notices
122 Using PHP Constants
123 Working with Numbers
125 Working with Character Strings

126 Single-quoted strings Versus double-quoted strings
127 Joining strings

128 Working with Dates and Times

128 Setting local time
129 Formatting a date
130 Storing a timestamp in a variable
131 Using dates with MySQL

132 Comparing Values

133 Making simple comparisons
135 Matching character strings to patterns

139 Joining Comparisons with and/or/xor
141 Adding Comments to Your Program

113 Adding a PHP Section to an HTML Page
- 115 Hello.html | Hello.php helloworld.php
  - note the address Hello.php points to starts with http://localhost
  - Hello.php uses the PHP echo statement to display the words Hello World!
  - the echo sttm also uses the paragraph tag in front of the words
116 Writing PHP Statements
119 Using PHP Variables (test01)
- 119 Naming a variable
  - all variable names have dollar signs in front of them
  - can be any length
  - can include letters, numbers, and underscores only
  - must begin with a letter or underscore, cannot begin with a number
  - uppercase and lowercase letters are not the same, $First and $first are two different variables
- 119 Creating and assigning values to variables
  - store numbers or strings into a variable by using the equal sign (=)
  - character strings are enclosed with double quotes while numbers are not
  - don't forget to use the semicolon at the end of the line
    - example: $variable1 = "one";
  - 120 unset($variable1); - the variable $variable1 no longer exists
  - 120-121 If you have a variable with an assigned value, the value remains until the page is done,
    even with html code in between two separate php sttms.
- 121 Dealing with notices
  - Notices are not the same as error msgs.
  - If you use a variable that does not exist, depending on how the error-message level for PHP is set, you might get a notice.
  - With a notice, the program continues to run.
  - A notice means that you are doing somethin unusual and it deems a second look at the code.
  - 121 You can insert an @ sign in front of a varaible to suppress a warning notice.
122 Using PHP Constants
- the format for setting a constant is as follows:
  - define ("constantname","contantvalue");
- examples:
  - define ("COMPANY","ABC Pet Store");
  - define ("AGE" ,29);
  - define ("ONE","one"); (test02) - test02 is just like test01 but uses the constant ONE.
    - note that constants are not preceded with a dollar sign
    - by convention, they are written in caps to make them easier to spot by the programmer, but that is not required.

123 Working with Numbers

**Arithmetic Operators**
Operator	Description
+	Add two numbers
-	Subtract the second number from the first number
*	Multiply two numbers
/	Divide the first number by the second number
%	Find the remainder when the first number is divided by the second number. This is called the modulus. Example: $a = 13 % 4, $a is set to 1. 13 divided by 4 is 3, with a remander of 1 because 13 minus 12 is 1.

123 you can do several arithmetic operations at once,
124 dollar amounts, if 10.00 is what you want PHP will display as 10
- to prevent that from happening, use the sprintf function
- $newvariablename = sprintf("%01.2f" $oldvariablename);
  - this statement reformats the number $oldvariablename
  - and stores it in the new format in $newvariablename (test03)
- If you want commas to separate thousands in your number, use the number_format function
- the following creates a dollar format with commas (test03)
- the 2 in number_format sets the decimal places to 2 in the test03 page.

125 Working with Character Strings

If a number is stored as a string, surrounded by double quotes, it cannot be used in arithmetic operations.
A string can be stored using single or double quotes, however if you use a single quote in the quote, such as 'Bob's house', that can create problems. The variable will think that Bob is all that is stored.
- To prevent that from happening, use the backslash (\) in front of the single quote like this:
- $strplace = 'Bob\'s house';
If you want a double quote to be presented the same way, use the backslash (\) in front of it.
126 Single-quoted strings Versus double-quoted strings (test04)
- handling variables
  - enclosing a variable in double quotes ensures that PHP will use the value of the variable.
  - enclosing a variable in single quotes ensures that PHP will use the literal variable name.
    - test04 demonstrates this.
- Starting a new line (test04)
  - the special characters \n tells PHP to start a new line.
  - inside of a string surrounded by double quotes this works properly
  - inside of a string surrounded by single quotes, \n is used literally.
  - Note this effects the page source from the browser, not the browser itself.
- Inserting a tab character (test04)
  - the special characters \t tells PHP to insert a tab character.
  - inside of a string surrounded by double quotes this works properly
  - inside of a string surrounded by single quotes, \t is used literally.
  - Note this effects the page source from the browser, not the browser itself.
127 Joining strings (test04)
- use the dot (.) to concatenate strings.
- the echo sttm outputs HelloWorld!
- Note no space between HelloWorld!
  - to do that change the third line to this:
  - $stringall = $string1." ".$string2;
- You can search strings and look for particular characters within strings, but that is covered in Chapter 7, pages xxx - xxx
- But I found stuff in Chapter 13, page 365

128 Working with Dates and Times

128 Setting local time (test05)
- I found the php.ini file in: C:\Program Files\xampp\php.ini
  - the semicolon was there, I had to take it out.
  - I went to http://www.php.net/manual/en/timezones.php
  - I entered America/New_York into the php.ini file
  - test05 has the function to display that.
- if you do not have access to the php.ini file, you can place the following in your program:
  - $def = date_default_timezone_set("timezonecode");

129 Formatting a date

the date function converts a date or time from the timestamp format into a format that you specify

the general format is: $mydate = date("format", $timestamp);

$timestamp is a variable with a timestamp stored into it.
if $timestamp is not included, the current time is from the operating system
thus you can get today's date with the following: $today = date("Y/m/d"); (test05)
the format is a string that specifies the date format you want stored in the $mydate variable
- example: "y-m-d" returns 06-08-10, while "M.d.Y" returns Aug.10.2006

hello

Date Format Symbols pages: 129-130
Symbol	Meaning	Example
F	Month in text, not abbreviated	January
M	Month in text, abbreviated	Jan
m	Month in numbers with leading zeros	02, 12
n	Month in numbers without leading zeros	2, 12
d	Day of the month; two digits with leading zeros	03, 30
j	Day of the month; two digits without leading zeros	3, 30
l	Day of the week in text, not abbreviated	Friday
D	Day of the week in text, abbreviated	Fri
w	Day of the week in numbers where 0 is Sunday, 1 is Monday, 6 is Saturday	1
Y	Year in four digits	2008
y	Year in two digits	02
g	Hour between 0 and 12 without leading zeros	2, 12
G	Hour between 0 and 24 without leading zeros	2, 15
h	Hour between 0 and 12 with leading zeros	01, 10
H	Hour between 0 and 24 with leading zeros	00, 23
i	Minutes	00, 59
s	Seconds	00, 59
a	am or pm in lowercase	am, pm
A	AM or PM in uppercase	AM, PM

130 Storing a timestamp in a variable

you can assign a timestamp with the current date and time to a variable with the following sttm:
- $today = time( ); (test05)

you can store specific timestamps by using the strtotime function with various keywords and abbreviations that are similar to English

you can create a timestamp for January 15, 2006 as follows:
$importantDate = strtotime("January 15, 2006"); (test05)

words and abbreviations strtotime recognizes
description	words and abbreviations
Month names	Twelve month names and abbreviations
Days of the week	Seven days and some abbreviations
Time units	year, month, fortnight, week, day, hour, minute, seconds, am, pm
Some useful English words	ago, now, last, next, this, tomorrow, yesterday
Plus and minus	+ or -
All numbers
Time zones	examples: gmt (Greenwich Mean Time), pdt (Pacific Daylight Time), akst (Alaska Standard Time)

You can combine the words and abbreviations in a wide varity of ways

the following sttms are all valid

**Valid Statements for strtotime** Page 131
$importantDate = strtotime("tomorrow"); #24 hours from now
$importantDate = strtotime("now + 24 hours");
$importantDate = strtotime("last saturday");
$importantDate = strtotime("2 weeks ago "); # current time
$importantDate = strtotime("next year gmt ");
$importantDate = strtotime("now + 24 hours");
$importantDate = strtotime("this 4am"); # 4 AM today

an example of using $importantDate = strtotime("today + 1 day"); and other examples: (test05)

131 Using dates with MySQL
- MySQL handles dates differently than string data.
- MySQL also handles dates differently than PHP.
- MySQL DATE data type columns expect dates with the year first, the month second and the day last.
  - the year can be yyyy or yy, the month can be mm or m, the day can be dd or d.
  - the parts can be separated by a hyphen(-), a forward slash(/), a dot(.) or a space.
- MySQL DATETIME data type columns expect both date and time.
  - the date is formatted as above, and followed by the time in the format hh:mm:ss.
- 132 Dates and times must be formatted in the correct MySQL format to store them in your database.
  - PHP functions can be used for formatting.
  - you can format today's date into MySQL format with the following sttm:
    - $today = date("Y-m-d");
  - You can format a specific date by using the sttm:
    - $importantDate = date("Y.m.d",strtotime("Jan 15 2008"));
  - You can than store the formatted date in the database with an SQL query like this:
    - UPDATE Member SET createDate="$today"
  - in some cases, MySQL date functions are easier to use than PHP sttms.
    - MySQL provides a function named DATEDIFF that computes the number of days between two dates, as follows
      - DATEDIFF(date1, date2)
    - the function returns the number of days from date2 to date1
    - to determine the number of days between a date in a table and the current date, you can do the following:
      - SELECT DATEDIFF(NOW(),Birth_date) FROM Customer
    - you can also use the function to return the number of days between dates that you provide as follows:
      - SELECT DATEDIFF('2004-1-15', '1997-12-30')
- 132 MySql provides many useful functions. All the date/time functions are described at:
  - http://dev.mysql.com/doc/refman/5.0/en/date-and-time-functions.html

132 Comparing Values

132 Conditional sttms ask, if something is true, your program does one thing,
- and if that condition is false, your program may do something else.

133 Making simple comparisons

simple comparisons compare one value to another.
PHP offers several ways to compare valuess

hello

**Comparing Values** Page 134
Comparison	Description
==	Are the two values equal ?
>	Is the first value larger than the second value ?
>=	Is the first value larger or equal to the second value ?
<	Is the first value smaller than the second value ?
<=	Is the first value smaller or equal to the second value ?
!=	Are the two values not equal to each other ?
<>	Are the two values not equal to each other ?

134 You can compare both numbers and strings.
- Strings are compared alphabetically, with uppercase characters coming before lower case characters.
  - SS comes before Sa
- Strings are compared based on their ASCII code
- Comparisons are used to test for a specific condition, an example follows:
- ```
 if ( $gender == "female" )
 {
 $tempGender = $gender;
 $swt = "on";
 }
```
- In this example if $gender equals "female" than set the two variables, otherwise, do not set those two variables.
- In order to set the two variables the condition has to be true. Note that the comparison operator is two equal signs. Look at the table above to see what it means.
- If you use one equal sign, $gender would be set to "female" and would always be true, use the correct comparison characters. It is a common mistake to use one equal sign instead of two.

135 Matching character strings to patterns
- Sometimes there is a need to find a pattern inside a string of data. PHP offers a varity of ways to do this.
- The following are twelve different ways of matching data in a string.

**Special Characters Used in Patterns** Page 136-137
Character	Meaning	Example	Match	Not a Match
^	Begining of line	^c	cat	my cat
$	End of line	c$	tic	stick
.	Any single character	. .	any string that contains at least two characters	a,i
?	Preceding character is optional	mea?n	mean, men	moan
( )	Groups literal characters into a string that must be matched exactly	m(ea)n	mean	men, mn
[ ]	Encloses a set of optional literal characters	m[ea]n	men, man	mean, mn
-	Represents all the characters between two characters	m[a-c]n	man, mbn, mcn	mdn, mun, maan
+	One or more of the preceding items	door[1-3]+	door111, door131	door, door55
*	Zero or more of the preceding items	door[1-3]*	door, door311	door4, door445
{ , }	The starting and ending numbers of a range of repetitions	a{2,5}	aa, aaaaa	a, xx3
\	The following character is literal	m\*n	m*n	men, mean
( \| \| )	A set of alternate strings	(Tom\|Tommy)	Tom, Tommy	Thomas, To

- 137 Literal and special characters can be combined to look for complex patterns.
- 137 Page 137and 138 has a sample list of patterns that work and don't work.
- here are some of the examples
  - ^[A-Z] . * Strings that begin with an uppercase letter
  - ^[0-9] {5} any string of five numbers
  - ^.+@.+\.com$ any string with @ embedded that ends in .com (looking for a type of email address)
- 138 You can compare a string to a pattern by using ereg. The format is as follows:
  - ereg("pattern", string);
- 138 Either pattern or string can be a literal as follows:
  - ereg("[0-9]*", "1234");
- 138 or can be stored in strings as follows:
  - ereg($pattern, $string);
- 139 to use ereg to check the name that a user typed in a form, compare the name to a pattern as follows
  - ereg("^[A-Za-z' -]+$", $name);
- 139 The pattern in this sttm does the following
  - uses ^ and $ to signify the begining and the end of te string. This means all the characters of the string must match the pattern.
  - Encloses all literal characters allowed allowed in the string in sqare brackets [ ]. No other characters allowed. Tha allowed characters are uppercase and lowercase letters, an apostrophe ( ' ), a blank space, and a hyphen ( - ). The hyphen is used at the end of the expression so it can be used to include all the characters between the A and the Z and the a and the z.
  - The plus sign means that the string can contain any number of the characters inside the square brackets [ ], but must contain at least one character.

139 Joining Comparisons with and/or/xor

Sometimes you have to check for more than one condition

PHP offers three ways to look for conditions

**Comparisons are connected by one of three words** Page 139
Comparison	Description	Order
and	both conditions are true	first
xor	one comparison is true, but not both	second
or	one or both comparisons are true	third

here are some examples

**Multiple Comparisons Page** Page 140
Condition	Is True If
$customer == "Smith" or $customer == "Jones"	The customer is named Smith or Jones
$customer == "Smith" and $custState == "NY"	The customer is named Smith and the state is NY
$customer == "Smith" or $custState == "NY"	The customer is named Smith or the state is NY
$customer == "Smith" xor $custState == "NY"	The customer is named Smith or the state is NY but not both
$customer != "Smith" and $custAge < 13	The customer's name is not Smith and the age is under 13

140 You can check on more than two compares, example:

141 Adding Comments to Your Program

This site is for the private use of my students. (2008)

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